Reza Bahoosh - Academia.edu (original) (raw)

Papers by Reza Bahoosh

In this paper we analyze the cycle-to-cycle fluctuations of peak pressure pmax and peak pressure ... more In this paper we analyze the cycle-to-cycle fluctuations of peak pressure pmax and peak pressure angle αpmax in a four-cylinder spark ignition engine. We examine the experimental time series of pmax and αpmax for four different equivalence ratio. Using standard statistical techniques such as return maps and Standard Deviation we show that depending equivalence ratio, there are significant differences in the fluctuations of pmax and αpmax. To evaluate the cycle-to-cycle fluctuations of SI combustion parameters, Standard Deviation (σ) of every parameter were calculated for every engine operating condition. Finally, we explain how the information on both pmax and αpmax can be used to develop optimal strategies for controlling the combustion process and improving engine performance. The results showed that φ=0.9 is enough to do accurate calculation of the average pressure cycle at various operation conditions of the engine.

The Analysis of the first law done by thermodynamic or fluid models is a suitable method for eval... more The Analysis of the first law done by thermodynamic or fluid models is a suitable method for evaluating the motor performance and sensitivity of its performance various parameters. This article is aimed at two-regional thermodynamic surveying of gasoline direct injection engines as well as comparing their pressure, fuel consumption, and the work produced in compression and expansion phases in these motors with port fuel injection engines. It would be concluded in this study that taking into account the fuel utilization reduction in direct injection engines, they also produce considerable work compared to port fuel injection motors.

AIP Conference Proceedings, 2007

In this article, a v2f model is employed to conduct a series of computations of incompressible ow... more In this article, a v2f model is employed to conduct a series of computations of incompressible ow in a periodic array of square cylinders simulating a porous media. A Galerkin/least-squares nite element formulation employing equal order velocity-pressure elements is used to discretize the governing equations. The Reynolds number is varied from 1000 to 84,000 and di erent values of porosities are considered in the calculations. Results are compared to the available data in the literature. The v2f model exhibits superior accuracy with respect to k " results and is closer to LES calculations. The macroscopic pressure gradients for all porosities studied showed a good agreement with Forchheimer-extended Darcy's law in the range of large Reynolds numbers.

A pickup's aerodynamics characteristic for reducing drag force and increasing negative lift i... more A pickup's aerodynamics characteristic for reducing drag force and increasing negative lift is studied; this study is performed to reduce fuel consumption and increase stability. The external flow devices such as a diffuser and a spoiler on the model which can change the direction of the airflow around the pickup to the desired direction are utilized. A diffuser at the rear end of the pick-up is studied to examine the effect of change of its length and angle on the aerodynamics characteristic of the Pickup. A spoiler length at the roof of the pickup spoiler as well as the change of its angle and the double spoiler are investigated; besides, the effect of the Bump's height on the tailgate of the pickup is studied. As a result of adding these devices to the pickup, increasing the diffuser length and angle, the drag coefficient and negative lift coefficient increase. In addition, the drag coefficient and negative lift coefficient will decrease if the spoiler length is increased...

Journal of Neurogastroenterology and Motility, 2017

Journal of the American College of Surgeons, 2018

INTRODUCTION: This project examined the relationship between surgical performance and motion-indu... more INTRODUCTION: This project examined the relationship between surgical performance and motion-induced fatigue, response speed, and errors during surgical resuscitative tasks onboard a US Naval vessel at high seas. Increased muscular effort due to ship motion increases energy expenditure. Resulting fatigue compromises task performance, increasing the risk of accidents. We hypothesize that motion-induced fatigue will negatively affect surgical performance. METHODS: Participants included 15 active-duty medical personnel, split into surgical teams. All personnel spent 15 days on US Naval Ship Brunswick and participated in daily surgical tasks to quantify the ability of medical teams to perform resuscitative surgical missions aboard US Naval ships at high sea states. Motion-induced fatigue was established by sleep analysis, Stanford Sleepiness Scale, and Fatigue Severity Scale. Resuscitative surgical tasks were graded for accuracy and efficiency. A Psychomotor Vigilance Task (PVT) was administered twice daily and participants alternated between 12-hour and 8-hour workdays. RESULTS: Twelve-hour days correlated with increased self-reported fatigue. Slowed PVT response correlated with fatigue, 12-hour days, time at sea, and calmer sea conditions. Increased PVT errors correlated with 12-hour days, rough conditions, and fatigue. Although PVT results suggested that fatigue affected the participants, fatigue and surgical performance were not correlated. CONCLUSIONS: The disparity between PVT scores and surgical performance while fatigued suggests that participants were conditioned to overcome fatigue to prioritize patient care and devoted less attention to the PVT. Quality of completion of repetitive tasks with low cognitive requirement can suffer during prolonged periods of activity at sea due to motion-induced fatigue or complacency.

Neurogastroenterology & Motility, 2017

Backgrounds: Chronic intestinal pseudo-obstruction (CIPO) is an intractable rare digestive diseas... more Backgrounds: Chronic intestinal pseudo-obstruction (CIPO) is an intractable rare digestive disease manifesting persistent small bowel distension without any mechanical cause. Intestinal decompression is a key treatment, but conventional method including a trans-nasal small intestinal tube is invasive and painful. Therefore, a less invasive and tolerable new decompression method is urgently desired. We conducted a pilot study and assessed the efficacy and safety of percutaneous endoscopic gastro-jejunostomy (PEG-J) decompression therapy in CIPO patients. Methods: Seven definitive CIPO patients (2 males and 5 females) were enrolled. All patients received PEG-J decompression therapy. The number of days with any abdominal symptoms in a month (NODASIM), body mass index (BMI), serum albumin level (Alb), and small intestinal volume before and after PEG-J were compared in all patients. Results: Percutaneous endoscopic gastro-jejunostomy was well tolerated and oral intake improved in all patients. NODASIM has significantly decreased (24.3 vs 9.3 days/ months) and BMI/Alb have significantly increased (14.9 vs 17.2 kg/m 2 and 2.6 vs 3.8 g/dL, respectively), whereas total volume of the small intestine has not significantly reduced (4.05 vs 2.59 L, P=.18). Reflux esophagitis and chemical dermatitis were observed in one case but was successfully treated conservatively. Conclusions & Inferences: Percutaneous endoscopic gastro-jejunostomy decompression therapy can contribute greatly to improvement of abdominal symptoms and nutritional status in CIPO patients. Although sufficient attention should be paid to acid reflux symptoms, PEG-J has the potential to be a non-invasive novel decompression therapy for CIPO available at home. However, accumulation of more CIPO patients and long-term observation are needed (UMIN000017574).

مدل ریاضی دوبعدی میکرو بایوحسگر ساندویچی با لایه­های حفره­دار و انتخابی، ارائه و تحلیل شده است. م... more مدل ریاضی دوبعدی میکرو بایوحسگر ساندویچی با لایه­های حفره­دار و انتخابی، ارائه و تحلیل شده است. مدل بایوحسگر حاضر شامل حفره­­هایی در ابعاد میکرو یا نانومتر است، که به‌صورت کامل یا بخشی از آن‌ها توسط آنزیم پر شده است. این مدل بر‌اساس سیستم معادلات واکنش- نفوذ، ارائه شده­است. معادلات حاکم ‌بر بایوحسگر ساندویچی حفره‌دار با در‌نظر گرفتن واکنش آنزیمی میکائیلیس- منتن، استخراج شده است و جملات غیر‌خطی مربوط به این اثر در‌نظر‌گرفته شد. با استخراج معادلات حاکم،‌ تأثیر هندسة حفره و سطح آنزیم در آن،‌ بر پاسخ بایوحسگر بررسی شد. در ادامه، معادلات با معرفی پارامترهای بی­بعد مناسب در حالت کلی بی­بعد‌شده ارائه شدند. سپس، معادلات حاکم به همراه شرایط مرزی آن‌ها، با استفاده از کد المان محدود در دو بعد حل شد. برای این منظور، سه هندسة متفاوت استوانه­ایی، مخروطی بالارونده و مخروطی پایین­رونده برای حفره­ها در‌نظر‌گرفته شد و تأثیر این هندسه­ها بر پاسخگویی بایوحسگر، در سطوح مختلف آنزیم مطالعه شد. پاسخ بایوحسگر، بر‌اساس تغییرات سطح آنزیم و تغییرات شیب مخروط استخراج شد. در بایوحسگر،‌ با افزایش سطح آنزیم برای ه...

Mechanics of Time-Dependent Materials, 2022

In this paper, the time-fractional oxygen diffusion has been simulated in a one-dimensional (1D) ... more In this paper, the time-fractional oxygen diffusion has been simulated in a one-dimensional (1D) corneal-contact lens (CL) system. Different CLs have been employed as Balafilcon, thin-and thick-Polymacon. It is assumed that homogeneous and isotropic porous mediums of cornea and CL is saturated with compressible oxygen. The computations of the timefractional derivations are done based on the Caputo method. The obtained results show that the fractional derivative order (FDO) severely affects pressure distribution in cornea and CL. Consequently, the magnitudes of post-lens-tear-film (PoLTF) pressure change due to diverse FDOs. Particularly, maximum changes have been observed in the results gained from the CLs with thicknesses more than 100 µm. The agreement of the results obtained from the time-fractional modeling with the experimental data compared to the standard diffusion modeling has been improved by more than 36%. Finally, it has been demonstrated that highthickness CLs can cause exist anomalous diffusion process in cornea tissue.

Numerical simulations of the airflow around a hatchback and a sedan vehicle without and with spoi... more Numerical simulations of the airflow around a hatchback and a sedan vehicle without and with spoilers are carried out, besides, its effect on drag and lift coefficients are investigated with and without crosswinds. The effects of crosswind on aerodynamic forces are considered and its results are compared with the case without considering the effects of crosswind. For this purpose, the steady-state three-dimensional Navier-Stokes equations are solved by the Simple Method. Moreover, for turbulence modeling, the Realizable k- model is implemented. The spoiler angle and its length are changed for both car models; furthermore, the effects of two spoilers on drag and lift coefficients are investigated in detail. All cases are simulated with and without crosswind. The results show that the impact of the spoiler for without crosswind conditions to decrease the lift coefficient in both models is significant; in addition, the drag coefficients are reduced for some cares. It can be concluded ...

Proceeding of Proceedings of CONV-14: International Symposium on Convective Heat and Mass Transfer. June 8 - 13, 2014, Kusadasi, Turkey, 2014

Korean Journal of Chemical Engineering

A 3D model for a section of cathode fuel cell comprised of a bipolar plate, a gas diffusion layer... more A 3D model for a section of cathode fuel cell comprised of a bipolar plate, a gas diffusion layer (GDL) and a catalyst layer was simulated. The diameter of the carbon fiber GDL is assumed to be the same; moreover, a new and simple method is introduced for the reconstruction of this layer numerically. This method gives the ability to model the heterogeneous and anisotropic structure of the GDL; furthermore, it allows easy implementation and provides realistic results with consideration of the lack of overlap between carbon fibers. The lattice Boltzmann method (LBM) was employed to simulate the flow and the electrochemical reaction. The impacts of changes in the activation potential and the GDL carbon fiber diameter on oxygen species and water vapor, as well as the electric current density distribution over the catalyst layer, were studied. The results showed that at higher values of the activation potential, the concentration of oxygen near the catalyst layer was lower. The current density over the catalyst layer also increased by increasing the activation potential; on the other hand, the mole fraction of water vapor in the cathode increased with the increase in the flow of gas products. Consequently, results indicated that the variation in the GDL carbon fiber diameter affects the distribution of reactants.

Applied Thermal Engineering, 2019

This paper presents investigation of heat transfer and fluid flow characteristics of water in a n... more This paper presents investigation of heat transfer and fluid flow characteristics of water in a novel cylindrical heat sink with helical minichannels experimentally. The heat sinks comprised of 36 minichannels with helix angles of 45, 60 and 90 (straight minichannels) deg, in addition the experimental tests have been carried out in the laminar flow regime (113

Received: 2017-10-13 Accepted: 2017-10-21 Availability analysis is an effective approach to study... more Received: 2017-10-13 Accepted: 2017-10-21 Availability analysis is an effective approach to studying energy conversion in systems and identifying inefficiency. In the present study, a single-zone model was used to examine energy performance parameters and heat release rates. The governing equation of availability analysis was applied in the model, and the possibility of using biodiesel produced from sunflower oil as diesel engine was investigated via mathematical simulation. The different exergy components of pure diesel fuel and pure biodiesel were compared at different crank angles. Results indicated that combining the examined diesel engine with biodiesel fuel would decrease the energy and exergy efficiencies by about 2.72% and 2.61%, respectively. As a result, work exergy and heat transfer exergy decrease and exhaust gas exergy and irreversibility would increase. When biodiesel is replaced with diesel fuel, carbon monoxide decreases, carbon dioxide formation increases, and nitro...

In this article, a two dimensional pore scale model of polymeric fuel cell, which is promising of... more In this article, a two dimensional pore scale model of polymeric fuel cell, which is promising of a clean and renewable energy production, is presented here. Let reactive gases behave as an ideal gas; inhomogeneous anisotropic structure of the gas diffusion layer, is contemplated as a random generated circular porous media. Lattice Boltzmann method is applied to inquire the fluid flow and mass transfer within the cathode microstructure. All parts of the cathode have the same temperature and the electrochemical reaction on the surface of the catalyst layer enters the solution as a boundary condition. Effects of the gas diffusion layer structure (carbon fibers diameters changes) on the flow of reactive gases, molar fraction of various oxygen species, and water vapor within the various parts of the gas diffusion layer as well as the electrical current density are investigated. The results indicate that by increasing the diameter of the carbon fibers in the gas diffusion layer within co...

This study numerically investigated heat transfer and fluid flow characteristics in a novel cylin... more This study numerically investigated heat transfer and fluid flow characteristics in a novel cylindrical heat sink with helical minichannels for the laminar flow of fluid with temperature-dependent properties. A finite volume method was employed to obtain the solution of governing equations. The effects of helical angle, channel aspect ratio, and Reynolds number, which were regarded as main parameters, were determined. The overall performance of the heat sink was also analyzed on the basis of the thermal performance factor and the augmentation entropy generation number. Results showed that a decrease in the channel helix angle and an increase in the channel aspect ratio and Reynolds number enhance the average heat transfer coefficient and pressure drop in the heat sink. The thermal performance factor and entropy generation minimization method revealed that an aspect ratio of 1.2 enables the best heat sink performance at all helix angles. When the helix angle decreases, performance in...

Availability analysis is performed as an effective way to study of energy conversion for systems ... more Availability analysis is performed as an effective way to study of energy conversion for systems to identify the inefficiency. In this paper, a Single-zone model has been used in order to study the energy performance parameters and heat release rates. The governing equation of availability analysis is applied in this model; in addition, the possibility of using biodiesel that obtained from sunflower oil in diesel engine is investigated by mathematical simulation. Moreover, the different exergy parts of pure diesel fuel and pure biodiesel are compared in any crank angle. Results indicate that, by running considered diesel engine with biodiesel fuel, energy and exergy efficiencies would decrease about 2.72 and 2.61 percent respectively. As a result, work exergy and heat transfer exergy decreases and exhaust gases exergy and irreversibility increases. Consequently, when biodiesel is replaced by diesel fuel, CO amount is decreased and CO2 and NOx formation would be increased because of ...

In this paper we analyze the cycle-to-cycle fluctuations of peak pressure pmax and peak pressure ... more In this paper we analyze the cycle-to-cycle fluctuations of peak pressure pmax and peak pressure angle αpmax in a four-cylinder spark ignition engine. We examine the experimental time series of pmax and αpmax for four different equivalence ratio. Using standard statistical techniques such as return maps and Standard Deviation we show that depending equivalence ratio, there are significant differences in the fluctuations of pmax and αpmax. To evaluate the cycle-to-cycle fluctuations of SI combustion parameters, Standard Deviation (σ) of every parameter were calculated for every engine operating condition. Finally, we explain how the information on both pmax and αpmax can be used to develop optimal strategies for controlling the combustion process and improving engine performance. The results showed that φ=0.9 is enough to do accurate calculation of the average pressure cycle at various operation conditions of the engine.

The Analysis of the first law done by thermodynamic or fluid models is a suitable method for eval... more The Analysis of the first law done by thermodynamic or fluid models is a suitable method for evaluating the motor performance and sensitivity of its performance various parameters. This article is aimed at two-regional thermodynamic surveying of gasoline direct injection engines as well as comparing their pressure, fuel consumption, and the work produced in compression and expansion phases in these motors with port fuel injection engines. It would be concluded in this study that taking into account the fuel utilization reduction in direct injection engines, they also produce considerable work compared to port fuel injection motors.

AIP Conference Proceedings, 2007

In this article, a v2f model is employed to conduct a series of computations of incompressible ow... more In this article, a v2f model is employed to conduct a series of computations of incompressible ow in a periodic array of square cylinders simulating a porous media. A Galerkin/least-squares nite element formulation employing equal order velocity-pressure elements is used to discretize the governing equations. The Reynolds number is varied from 1000 to 84,000 and di erent values of porosities are considered in the calculations. Results are compared to the available data in the literature. The v2f model exhibits superior accuracy with respect to k " results and is closer to LES calculations. The macroscopic pressure gradients for all porosities studied showed a good agreement with Forchheimer-extended Darcy's law in the range of large Reynolds numbers.

A pickup's aerodynamics characteristic for reducing drag force and increasing negative lift i... more A pickup's aerodynamics characteristic for reducing drag force and increasing negative lift is studied; this study is performed to reduce fuel consumption and increase stability. The external flow devices such as a diffuser and a spoiler on the model which can change the direction of the airflow around the pickup to the desired direction are utilized. A diffuser at the rear end of the pick-up is studied to examine the effect of change of its length and angle on the aerodynamics characteristic of the Pickup. A spoiler length at the roof of the pickup spoiler as well as the change of its angle and the double spoiler are investigated; besides, the effect of the Bump's height on the tailgate of the pickup is studied. As a result of adding these devices to the pickup, increasing the diffuser length and angle, the drag coefficient and negative lift coefficient increase. In addition, the drag coefficient and negative lift coefficient will decrease if the spoiler length is increased...

Journal of Neurogastroenterology and Motility, 2017

Journal of the American College of Surgeons, 2018

INTRODUCTION: This project examined the relationship between surgical performance and motion-indu... more INTRODUCTION: This project examined the relationship between surgical performance and motion-induced fatigue, response speed, and errors during surgical resuscitative tasks onboard a US Naval vessel at high seas. Increased muscular effort due to ship motion increases energy expenditure. Resulting fatigue compromises task performance, increasing the risk of accidents. We hypothesize that motion-induced fatigue will negatively affect surgical performance. METHODS: Participants included 15 active-duty medical personnel, split into surgical teams. All personnel spent 15 days on US Naval Ship Brunswick and participated in daily surgical tasks to quantify the ability of medical teams to perform resuscitative surgical missions aboard US Naval ships at high sea states. Motion-induced fatigue was established by sleep analysis, Stanford Sleepiness Scale, and Fatigue Severity Scale. Resuscitative surgical tasks were graded for accuracy and efficiency. A Psychomotor Vigilance Task (PVT) was administered twice daily and participants alternated between 12-hour and 8-hour workdays. RESULTS: Twelve-hour days correlated with increased self-reported fatigue. Slowed PVT response correlated with fatigue, 12-hour days, time at sea, and calmer sea conditions. Increased PVT errors correlated with 12-hour days, rough conditions, and fatigue. Although PVT results suggested that fatigue affected the participants, fatigue and surgical performance were not correlated. CONCLUSIONS: The disparity between PVT scores and surgical performance while fatigued suggests that participants were conditioned to overcome fatigue to prioritize patient care and devoted less attention to the PVT. Quality of completion of repetitive tasks with low cognitive requirement can suffer during prolonged periods of activity at sea due to motion-induced fatigue or complacency.

Neurogastroenterology & Motility, 2017

Backgrounds: Chronic intestinal pseudo-obstruction (CIPO) is an intractable rare digestive diseas... more Backgrounds: Chronic intestinal pseudo-obstruction (CIPO) is an intractable rare digestive disease manifesting persistent small bowel distension without any mechanical cause. Intestinal decompression is a key treatment, but conventional method including a trans-nasal small intestinal tube is invasive and painful. Therefore, a less invasive and tolerable new decompression method is urgently desired. We conducted a pilot study and assessed the efficacy and safety of percutaneous endoscopic gastro-jejunostomy (PEG-J) decompression therapy in CIPO patients. Methods: Seven definitive CIPO patients (2 males and 5 females) were enrolled. All patients received PEG-J decompression therapy. The number of days with any abdominal symptoms in a month (NODASIM), body mass index (BMI), serum albumin level (Alb), and small intestinal volume before and after PEG-J were compared in all patients. Results: Percutaneous endoscopic gastro-jejunostomy was well tolerated and oral intake improved in all patients. NODASIM has significantly decreased (24.3 vs 9.3 days/ months) and BMI/Alb have significantly increased (14.9 vs 17.2 kg/m 2 and 2.6 vs 3.8 g/dL, respectively), whereas total volume of the small intestine has not significantly reduced (4.05 vs 2.59 L, P=.18). Reflux esophagitis and chemical dermatitis were observed in one case but was successfully treated conservatively. Conclusions & Inferences: Percutaneous endoscopic gastro-jejunostomy decompression therapy can contribute greatly to improvement of abdominal symptoms and nutritional status in CIPO patients. Although sufficient attention should be paid to acid reflux symptoms, PEG-J has the potential to be a non-invasive novel decompression therapy for CIPO available at home. However, accumulation of more CIPO patients and long-term observation are needed (UMIN000017574).

مدل ریاضی دوبعدی میکرو بایوحسگر ساندویچی با لایه­های حفره­دار و انتخابی، ارائه و تحلیل شده است. م... more مدل ریاضی دوبعدی میکرو بایوحسگر ساندویچی با لایه­های حفره­دار و انتخابی، ارائه و تحلیل شده است. مدل بایوحسگر حاضر شامل حفره­­هایی در ابعاد میکرو یا نانومتر است، که به‌صورت کامل یا بخشی از آن‌ها توسط آنزیم پر شده است. این مدل بر‌اساس سیستم معادلات واکنش- نفوذ، ارائه شده­است. معادلات حاکم ‌بر بایوحسگر ساندویچی حفره‌دار با در‌نظر گرفتن واکنش آنزیمی میکائیلیس- منتن، استخراج شده است و جملات غیر‌خطی مربوط به این اثر در‌نظر‌گرفته شد. با استخراج معادلات حاکم،‌ تأثیر هندسة حفره و سطح آنزیم در آن،‌ بر پاسخ بایوحسگر بررسی شد. در ادامه، معادلات با معرفی پارامترهای بی­بعد مناسب در حالت کلی بی­بعد‌شده ارائه شدند. سپس، معادلات حاکم به همراه شرایط مرزی آن‌ها، با استفاده از کد المان محدود در دو بعد حل شد. برای این منظور، سه هندسة متفاوت استوانه­ایی، مخروطی بالارونده و مخروطی پایین­رونده برای حفره­ها در‌نظر‌گرفته شد و تأثیر این هندسه­ها بر پاسخگویی بایوحسگر، در سطوح مختلف آنزیم مطالعه شد. پاسخ بایوحسگر، بر‌اساس تغییرات سطح آنزیم و تغییرات شیب مخروط استخراج شد. در بایوحسگر،‌ با افزایش سطح آنزیم برای ه...

Mechanics of Time-Dependent Materials, 2022

In this paper, the time-fractional oxygen diffusion has been simulated in a one-dimensional (1D) ... more In this paper, the time-fractional oxygen diffusion has been simulated in a one-dimensional (1D) corneal-contact lens (CL) system. Different CLs have been employed as Balafilcon, thin-and thick-Polymacon. It is assumed that homogeneous and isotropic porous mediums of cornea and CL is saturated with compressible oxygen. The computations of the timefractional derivations are done based on the Caputo method. The obtained results show that the fractional derivative order (FDO) severely affects pressure distribution in cornea and CL. Consequently, the magnitudes of post-lens-tear-film (PoLTF) pressure change due to diverse FDOs. Particularly, maximum changes have been observed in the results gained from the CLs with thicknesses more than 100 µm. The agreement of the results obtained from the time-fractional modeling with the experimental data compared to the standard diffusion modeling has been improved by more than 36%. Finally, it has been demonstrated that highthickness CLs can cause exist anomalous diffusion process in cornea tissue.

Numerical simulations of the airflow around a hatchback and a sedan vehicle without and with spoi... more Numerical simulations of the airflow around a hatchback and a sedan vehicle without and with spoilers are carried out, besides, its effect on drag and lift coefficients are investigated with and without crosswinds. The effects of crosswind on aerodynamic forces are considered and its results are compared with the case without considering the effects of crosswind. For this purpose, the steady-state three-dimensional Navier-Stokes equations are solved by the Simple Method. Moreover, for turbulence modeling, the Realizable k- model is implemented. The spoiler angle and its length are changed for both car models; furthermore, the effects of two spoilers on drag and lift coefficients are investigated in detail. All cases are simulated with and without crosswind. The results show that the impact of the spoiler for without crosswind conditions to decrease the lift coefficient in both models is significant; in addition, the drag coefficients are reduced for some cares. It can be concluded ...

Proceeding of Proceedings of CONV-14: International Symposium on Convective Heat and Mass Transfer. June 8 - 13, 2014, Kusadasi, Turkey, 2014

Korean Journal of Chemical Engineering

A 3D model for a section of cathode fuel cell comprised of a bipolar plate, a gas diffusion layer... more A 3D model for a section of cathode fuel cell comprised of a bipolar plate, a gas diffusion layer (GDL) and a catalyst layer was simulated. The diameter of the carbon fiber GDL is assumed to be the same; moreover, a new and simple method is introduced for the reconstruction of this layer numerically. This method gives the ability to model the heterogeneous and anisotropic structure of the GDL; furthermore, it allows easy implementation and provides realistic results with consideration of the lack of overlap between carbon fibers. The lattice Boltzmann method (LBM) was employed to simulate the flow and the electrochemical reaction. The impacts of changes in the activation potential and the GDL carbon fiber diameter on oxygen species and water vapor, as well as the electric current density distribution over the catalyst layer, were studied. The results showed that at higher values of the activation potential, the concentration of oxygen near the catalyst layer was lower. The current density over the catalyst layer also increased by increasing the activation potential; on the other hand, the mole fraction of water vapor in the cathode increased with the increase in the flow of gas products. Consequently, results indicated that the variation in the GDL carbon fiber diameter affects the distribution of reactants.

Applied Thermal Engineering, 2019

This paper presents investigation of heat transfer and fluid flow characteristics of water in a n... more This paper presents investigation of heat transfer and fluid flow characteristics of water in a novel cylindrical heat sink with helical minichannels experimentally. The heat sinks comprised of 36 minichannels with helix angles of 45, 60 and 90 (straight minichannels) deg, in addition the experimental tests have been carried out in the laminar flow regime (113

Received: 2017-10-13 Accepted: 2017-10-21 Availability analysis is an effective approach to study... more Received: 2017-10-13 Accepted: 2017-10-21 Availability analysis is an effective approach to studying energy conversion in systems and identifying inefficiency. In the present study, a single-zone model was used to examine energy performance parameters and heat release rates. The governing equation of availability analysis was applied in the model, and the possibility of using biodiesel produced from sunflower oil as diesel engine was investigated via mathematical simulation. The different exergy components of pure diesel fuel and pure biodiesel were compared at different crank angles. Results indicated that combining the examined diesel engine with biodiesel fuel would decrease the energy and exergy efficiencies by about 2.72% and 2.61%, respectively. As a result, work exergy and heat transfer exergy decrease and exhaust gas exergy and irreversibility would increase. When biodiesel is replaced with diesel fuel, carbon monoxide decreases, carbon dioxide formation increases, and nitro...

In this article, a two dimensional pore scale model of polymeric fuel cell, which is promising of... more In this article, a two dimensional pore scale model of polymeric fuel cell, which is promising of a clean and renewable energy production, is presented here. Let reactive gases behave as an ideal gas; inhomogeneous anisotropic structure of the gas diffusion layer, is contemplated as a random generated circular porous media. Lattice Boltzmann method is applied to inquire the fluid flow and mass transfer within the cathode microstructure. All parts of the cathode have the same temperature and the electrochemical reaction on the surface of the catalyst layer enters the solution as a boundary condition. Effects of the gas diffusion layer structure (carbon fibers diameters changes) on the flow of reactive gases, molar fraction of various oxygen species, and water vapor within the various parts of the gas diffusion layer as well as the electrical current density are investigated. The results indicate that by increasing the diameter of the carbon fibers in the gas diffusion layer within co...

This study numerically investigated heat transfer and fluid flow characteristics in a novel cylin... more This study numerically investigated heat transfer and fluid flow characteristics in a novel cylindrical heat sink with helical minichannels for the laminar flow of fluid with temperature-dependent properties. A finite volume method was employed to obtain the solution of governing equations. The effects of helical angle, channel aspect ratio, and Reynolds number, which were regarded as main parameters, were determined. The overall performance of the heat sink was also analyzed on the basis of the thermal performance factor and the augmentation entropy generation number. Results showed that a decrease in the channel helix angle and an increase in the channel aspect ratio and Reynolds number enhance the average heat transfer coefficient and pressure drop in the heat sink. The thermal performance factor and entropy generation minimization method revealed that an aspect ratio of 1.2 enables the best heat sink performance at all helix angles. When the helix angle decreases, performance in...

Availability analysis is performed as an effective way to study of energy conversion for systems ... more Availability analysis is performed as an effective way to study of energy conversion for systems to identify the inefficiency. In this paper, a Single-zone model has been used in order to study the energy performance parameters and heat release rates. The governing equation of availability analysis is applied in this model; in addition, the possibility of using biodiesel that obtained from sunflower oil in diesel engine is investigated by mathematical simulation. Moreover, the different exergy parts of pure diesel fuel and pure biodiesel are compared in any crank angle. Results indicate that, by running considered diesel engine with biodiesel fuel, energy and exergy efficiencies would decrease about 2.72 and 2.61 percent respectively. As a result, work exergy and heat transfer exergy decreases and exhaust gases exergy and irreversibility increases. Consequently, when biodiesel is replaced by diesel fuel, CO amount is decreased and CO2 and NOx formation would be increased because of ...